Wisconsin Loon Population Survey

2015 Loon Population Survey (WLPS)

Every five years since 1985, LoonWatch has conducted a one-day loon survey on a pre-selected group of lakes to estimate the size and distribution of Wisconsin's Common Loon population. Volunteer observers visit a lake or lakes on one day in July between 5 a.m. and 10 a.m. to count both adults and chicks. This information is then used to estimate the number of breeding adults and the number of chicks produced. Over time, the survey tells us the trend in the state's loon population-whether it is stable, increasing or declining.

The next loon population survey will take place on July 18, 2015 between the hours of 5 a.m. and 10 a.m. Volunteers will be needed to go out to each of over 250 randomly selected lakes in northern Wisconsin and count all adult loons and chicks. Volunteers are encouraged to use canoes/kayaks or boats to survey their lake, although surveying from the lake shore is also acceptable. Why on July 18th between 5 and 10 A.M.? Because to get the most accurate estimation of the loon population possible, we must minimize the possibility that a loon counted on one lake could fly to another lake and be counted again. The count is on July 16th because by this time loons typically have hatched their chicks. There will be a rain date on July 25, 2015, if needed.

To volunteer, please check back in 2014 to sign up for the 2015 survey. Return to this site in February/March for the Summary of Results from the Special 2011 Survey.

The 2011 Wisconsin Loon Population Survey
A special 2011 survey was conducted because of fears that the 2010 Gulf oil spill might have adversely affected loon populations that winter in the Gulf of Mexico. The results for the 2011 Wisconsin Loon Population Survey are in, and are different than what we were expecting.  The good news is that the 2011 survey doesn't suggest any sudden drop in the WI loon population following the Gulf oil spill.  However, the results indicate that the adult loon population was much larger than we were anticipating.  We suspect a couple reasons for this result.  We had a smaller volunteer turnout in 2011 (156 lakes sampled) than in 2010 (232 lakes sampled).  The data also suggests that volunteers were less likely to resurvey lakes where few to no loons had been seen in 2010.  This may have skewed the results to produce a larger population estimate than we expected.  In spite of those issues, the survey doesn't indicate a decline (population estimates for the same lakes sampled in both 2010 and 2011are quite similar).  Because juvenile loons remain in the Gulf of Mexico for 2 to 3 years before returning to their northern lakes, the 2015 survey may reveal whether there are long-term consequences to the oil spill.

We are planning to do the 2015 survey, and plan to recruit a larger volunteer turnout than in 2011, making sure that, as many lakes are included in the survey as possible.  Please contact LoonWatch if you would like to participate in the 2015 survey.

Summary of Results from 2010

July 17, 2010 marked the sixth Wisconsin Loon Population Survey (WLPS) and it may be our best effort yet. Volunteers surveyed 244 of the 258 pre-selected lakes. This is the most lakes ever visited during this survey's 25-year history. The most lakes surveyed previously was 225 in 2005.

The analysis results are in and the outlook for Wisconsin's loon population looks good. The adult loon population for 2010 was estimated at approximately 4,000 and chick population was estimated at approximately 600. This represents a significant adult population increase over the 3,373 adults and slight chick population decrease below the 805, estimated in 2005. Thus, 2010 had the largest adult loon population estimate since the survey started in 1985. Why isn't the chick population the highest as well? This appears to be primarily linked to increased territorial aggression. As the loon population grows, they are using sub-prime nesting habitat and are fighting each other for the prime nesting habitat. Both of these behaviors lead to less chick productivity. Loons who do not have a territory, often referred to as prospecting loons, will attack a loon on a prime territory in an attempt to win the territory and the mate that is there. Typically these are male on male or female on female battles, and if an intruding loon wins, it will mean that the current nest or chicks will be abandoned.

Another trend we saw in 2010 was the presence of large groups of loons on lakes. Groups of loons are typically loons that don't have a territory or have lost their nest or chick early. These loons typically return to their territorial lake late each evening, but leave again in the morning to feed in groups. Working together to corral fish is one advantage that loons in groups have over individuals.

A full report of the Wisconsin Loon Population Survey will be distributed to volunteers who helped with the surveys and will be available online in the near future. Thank you to the many volunteers who took the time to participate in the survey. We could not have done it without you! Please consider registering as soon as possible for the special, post-oil spill Wisconsin Loon Population on Saturday, July 16, 2011 to help assess if there were significant impacts to the population over the winter and fall.

Summary of Results from 2005
The results indicate that the outlook for Wisconsin's loon population looks good. The adult loon population for 2005 was estimated at 3,373 (±495) and chick population was estimated at 805 (±218). This represents a marginal adult population increase over 3,131 adults estimated in 2000 and significant chick population increase over 462 in 2000. Thus 2005 had the largest loon population estimate since the survey started in 1985.

We also look at what proportion of the loon population comes from four lake size classes. When the two smaller lake classes (25-149 acres) were combined and the two larger lake classes (150+ acres) were combined, an interesting pattern emerges over time. In 1985, 20% of the population was found on the large lakes and 80% on the small lakes. As of 2005, this ratio was about equal with approximately half of the population on small lakes and half on large lakes. We don't collect any other data with this survey to correlate our population numbers to lake factors that may be the cause for this shift. We can speculate that something has changed on small lakes that make them last attractive to loons or something has changed on the large lakes that make them more attractive than in the past. One is left wondering if a shift toward increased shoreline development on small lakes over the past 20 years might not be at least part of the cause. Regardless, our loon population seems to be adapting to these changes as the population seems to be doing well.

Summary of Results from 2000
During the 2000 survey, volunteers observed 223 adults and 34 chicks on 151 lakes in 25 counties. Using these data, the 2000 Wisconsin loon population was estimated at 3,131 adults and 462 chicks. The 2000 adult population estimate was significantly larger than the 1985 estimate of 2,358. The chick population estimate was the lowest on record but did not differ significantly from any of the previous surveys. The adult Common Loon population in Wisconsin appears to be strong and may even be growing. Though it would be inaccurate to view the 2000 survey data as a sign that loon productivity in Wisconsin is declining overall. It is important to note that moderate to large lakes are an important component of the loon's breeding habitat, and research by the Wisconsin DNR has found that these areas are under the greatest pressure from development and recreational use.

Excerpts of survey results from: Gostomski, Theodore J. and Paul W. Rasmussen. 2001. Results of the 2000 Common Loon Survey in Wisconsin. Passenger Pigeon. 63 (1&2): 15-25.

LoonWatch
1411 Ellis Avenue
Ashland, WI 54806
(715) 682-1220
LoonWatch@northland.edu